• Korean Journal of Applied Biomechanics
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• v.17 no.1
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• pp.121-127
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• 2007

Muscle force produced by muscle fibers is transmitted to bones via tendinous structures(aponeuroses and tendon), resulting in joint(s) movement. As force-transmitting elements, mechanical behavior of aponeuroses and tendon are closely related with the function of muscle-tendon complex. The purpose of this study was to determine strain characteristics of aponeuroses for in-vivo human soleus muscle during submaximal voluntary contractions using an advanced medical imaging technique, velocity-encoded phase-contrast magnetic resonance imaging (VE-PC MRI). VE-PC MRI of the soleus muscle-tendon complex was acquired during submaximal isometric plantarflexion contraction-relaxation cycle (n = 7), using 3.0T Trio MRI scanner(Siemens AG, Malvern, MA). From the VE-PC MRI containing the tissue velocity in superior-inferior direction, twenty regions of interest(20 ROI; 10 on the anterior aponeurosis and 10 on the posterior aponeurosis) were tracked. During the isometric plantarflexion contraction-relaxation cycle, velocity and displacement profiles were different between the anterior and posterior aponeuroses, indicating heterogeneous strain behavior along the length of the leg. The anterior aponeurosis elongated while the posterior aponeurosis shortened during the initial phase of the contraction. Moreover, strain behavior of the posterior aponeurosis was different from that of the Achilles tendon. Possible explanation for the observed variations in strain behavior of aponeuroses was investigated with morphological assessment of the soleus muscle and it was found that the intramuscular tendinous structures significantly vary among subjects. In conclusion, the heterogeneous mechanical behavior of the soleus aponeuroses and the Achilles tendon suggests that the complexity of skeletal muscle-tendon complex should be taken into consideration when modeling the complex for better understanding of its functions.

• Biomolecules & Therapeutics
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• v.4 no.2
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• pp.167-173
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• 1996

This study was undertaken to evaluate a behavior-electroencephalogram (EEG) pattern relationship in pilocarpine- and kainic acid-induced convulsions of rats. Also we intended to examine the effect of a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist, MK-801, and diazepam on the pilocarpine-induced behavioral and electrical seizures in rats. The electrical activities at frontal and hippocampal areas and behavior activities were measured in freely moving rats. At the beginning of the experiments, the rats displayed an exploratory behavior. This awake and moving phase with a low amplitude, irregular, 4-10 Hz wave was followed by a still phase. Pilocarpine (400 mg/kg, i.p.) and kainic acid (0.5 mg/kg, i.c.v.) induced tonic and clonic seizures. The pilocarpine-induced change in electrical activities exhibited a weak correlation with behavioral convulsion at all stages. The amplitude and duration of the electrical response were not linear with the degree of behavioral score. An application of MK-801 (dizocilpine, 7.5 mg/kg) did not affect the amplitudes of the convulsant-induced electrical activities, though the same dose of this drug caused the deformation of the electrical pattern. There was no effect of MK-801 on the behavioral and electrical activities as expected. Diazepam (1 mg/kg) did not affect the amplitude of the electrical activities induced by pilocarpine but changed the pattern of these activities. Our study shows that there is no linear relationship between degree of behavior and amplitude of electrical activities of convulsants. This may indicate that the NMDA receptor stimulation can be processed by the neocortical or hippocampal network in a different way between behavioral and electrical activities.

• Journal of Aerospace System Engineering
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• v.16 no.4
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• pp.35-44
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• 2022

The study on the wake vortex behavior during the aircraft's take-off and landing flight phase is critical to the flight safety of the aircraft, following close behind and the economy of the airport. The study on the wake vortex behavior should include the understanding of the ground effect on the behavior of the multiple wake vortices, generated from aircraft during the take-off and landing flight phase. In thia study, numerical schemes that can consider the ground effect were devised, by applying a vorticity boundary condition and an image method into the existing two-dimensional Fourier-spectral method. The present method was validated by comparing the present results, with the computed and measured data in the published literature. It was shown that the present method can predict the generation and behavior of the secondary vortex near the ground with reasonable accuracy. In future, the effect of the atmospheric conditions such as the stratification and the wind shear on the behavior of the vortex pair will be studied.

• Sleep Medicine and Psychophysiology
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• v.18 no.1
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• pp.23-28
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• 2011

Objectives: REM sleep behavior disorder (RBD) has received little attention in epidemiologic studies. This study aimed to determine the prevalence of probable REM sleep behavior disorder (pRBD) in the elderly population and its clinical features. Methods: A random sample of 1,588 was selected from a roster of 14,050 elderly population living in Osan city. The subjects were asked to fill out the REM sleep behavior disorder screening questionnaire (RBDSQ). Subjects whose score were 5 or higher on RBDSQ underwent a diagnostic phase of person-to-person assessment by experts in RBD. Results: Among 1,588 subjects, 886 elderly subjects participated in the screening phase and 123 subjects were assessed in the diagnostic phase. Eleven subjects were diagnosed as having pRBD, so prevalence was 1.5% (95% CI=0.70-2.30%). The frequency of depression and cognitive decline was significantly increased in patients with pRBD compared to subjects without pRBD, and there was no difference in sleep disturbances between two groups. Conclusions: Probable REM sleep behavior disorder is not rare in the elderly but frequently under-recognized. More attention should be paid to evaluation and treatment of RBD.

• Korean Journal of Materials Research
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• v.4 no.8
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• pp.906-914
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• 1994

Plastic behavior of two-phase intermetallic compounds based on $LI_{2}$-type $(Al, Cr)_3$ Ti was investigated using compression test at R.T. and 77K. $LI_{2}$ single phase alloys and two-phase alloys consisting of mainly $LI_{2}$ phase and a few or 20% second phases were selected from AI-Ti-Cr phase diagram. In general, compared with Llz single phase, two-phase alloys consisting of 20% second phase showed relatively high yield strength and poor ductility. Among the alloys, however, AI-21Ti-23Cr alloy consisting of 20% $Cr_{2}Al$ phase showed available ductility as well as high yield strength. Plastic behavior of $LI_{2}$ single phase alloys and two-phase alloys consisting of a few% $Cr_{2}Al$ was also investigated. Homogenization of arc melted ingots substantially reduced the amount of second phases but introduced extensive pore. When Cr content increased in $Ll_{2}$ single phase alloys after the homogenization, the volume fraction of pore in the alloys decreased, and no residual pore was observed in two-phase alloys consisting of a few% $Cr_{2}Al$ phase. Environmental effect on the ductility of the alloys was investigated using compression test at different strain rates($1.2 \times 10^{-4}/s$ and $1.2 \times 10^{-2}/s$). Environmental embrittlement was least significant in A1-25Ti-10Cr alloy consisting of LIZ single phase among the alloys tested in this study. However, based on the combined estimation of the pore formation, environmental embrittlement and ingot cast structure, AI-21Ti-23Cr alloy consisting of 20% $Cr_{2}Al$ as the second phase is expected to show the best tensile elongation behavior.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.10
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• pp.1184-1192
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• 2004

Experimental investigations were carried out in an atmospheric pressure, optically accessible and laboratory-scale dump combustor operating on methane gas. The objective of this study was to obtain the phase-resolved gas temperatures at different phases of the oscillating pressure cycle during unstable combustion. CARS temperature measurements were made at several spatial locations under lean premixed conditions to get the information on temperature field within the combustor. Also the effect of incomplete fuel-air mixing on phase-resolved temperature fluctuation was investigated. Results including phase-resolved averaged temperature, normalized standard deviation and temperature probability distribution functions (PDFs) were provided in this paper. Temperature PDFs gave an insight on the flame behavior. And strong correlation between phase-resolved temperature profile and pressure cycle was observed. Results of the phase-resolved high temperature gave an additional information on the perturbation of equivalence ratio at flame as well as the effect of mixing quality on NOx emission characteristics.

• Journal of the Korean Applied Science and Technology
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• v.15 no.2
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• pp.25-32
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• 1998

The emulsion stability of W/O emulsion prepared by D phase emulsification during storage and handling is studied by using phase diagrams. The process of D phase emulsification begins with the formation of isotropic surfactant solution, followed by formation of oil-in-surfactant (O/D) gel emulsion by dispersion of octamethylcyclotetrasiloxane(OMCS) in the surfactant solution. Polyols were essential components for this purpose. To understand the function of polyols, the solution behavior of nonionic surfactant/oil/water/polyol systems were investigated by the ternary phase diagrams of polyoxyethylene oleyl ether/OMCS/propylene glycol(PG) aqueous solutions. The addition of PG increased the solubility of oil in the isotropic surfactant phase. D phase emulsification method has been applied to a new type of cosmetics. By using this emulsification technique, O/W emulsion were formed without a need for adjust of HLB. Fine and stable W/O emulsions were prepared by D phase emulsion.

• 한국연소학회:학술대회논문집
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• 2003.12a
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• pp.97-102
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• 2003

Experimental investigations were carried out in an atmospheric pressure, optically accessible and laboratory-scale dump combustor operating on natural gas. The objective of this study is to obtain the phase-resolved gas temperatures at different phases of the oscillating pressure cycle during unstable combustion. CARS temperature measurements were made at several spatial locations under lean premixed conditions to get the information on temperature field within the combustor. Also the effect of incomplete fuel-air mixing on phase-resolved temperature fluctuation was investigated. Results including phase-resolved averaged temperature, normalized standard deviation and temperature probability distribution functions (PDFs) were provided in this paper. Temperature PDFs give an insight on the flame behavior. And strong correlation between phase-resolved temperature profile and pressure cycle was observed. Results of the phase-resolved high temperature give an additional information on the perturbation of equivalence ratio at flame as well as the effect of mixing quality on NOx emission characteristics.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.2
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• pp.53-59
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• 2021

Due to high specific strength and low density, AZ series magnesium alloys have been receiving high interest as a lightweight material. However, their industrial application is limited due to the phenomenon that the strength decreases at elevated temperature by the occurrence of softening effect because of the Mg17Al12 phase decomposition. To solve this problem, many research were conducted to increase the high-temperature strength by forming a thermal stable second-phase component by adding new elements to the AZ magnesium. Especially, adding Ca to AZ magnesium has been reported that Ca forms the new second-phase. However, studies about the analysis of decomposition or precipitation temperature, formation composition, and components to understand the formation behavior of these precipitated phases are still insufficient. Therefore, the effect of Ca addition to AZ61 on the phase change and microstructure of the alloy during annealing was investigated. As a result of analysis of the initial and heat-treated specimen, AZ61 formed α-Mg matrix and precipitated phase of Mg17Al12, and AZX611 formed one more type of precipitated phase, Al2Ca. Also, Al2Ca was thermal stable at high temperatures. And after annealing, the laves phase was decomposed to under 10 ㎛ size and distributed in matrix.

• Nuclear Engineering and Technology
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• v.54 no.2
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• pp.554-564
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• 2022

The natural circulation phenomena occurring in fully integrated nuclear reactors are associated with a unique formation mechanism. The phenomenon results from a structural feature of these reactors involving upward flow from the core, located in the central-bottom region of a single vessel, and downward flow to the steam generator in the annulus region. In this study, to understand the natural circulation in a single vessel involving a multi-layered flow path, single-phase and two-phase natural circulation tests were performed using the SMART-ITL facility, and validation analysis of the TASS/SMR-S code was performed by comparing the corresponding test results. Three single-phase natural circulation tests were sequentially conducted at 15%, 10%, and 5% of full-scaled core-power without RCP operation, following which a two-phase natural circulation test was successively conducted with an artificial discharge of coolant inventory. The simulation capability of the TASS/SMR-S code with respect to the natural circulation phenomena was validated against the test results, and somewhat conservative but reasonably comparative results in terms of overall thermalhydraulic behavior were shown.